The present invention relates generally to cooling systems for electrical equipment. More particularly, the present invention relates to a unique series-parallel fan system for cooling electrical equipment.
Many electrical devices require forced air cooling to ensure that the devices remain in their ideal operating temperature range. Fans are commonly used to provide cooling. In a typical system, one or more fans will induce airflow over one or more electrical devices, either by negative pressure (suction) or by positive pressure. The fans and electrical devices may be enclosed in housings that help contain and guide the airflow, thereby increasing the efficiency of the cooling system. Such systems may have fans in a parallel, in which case the fans each fan blows a separate mass of air to provide a combined airflow, or the system may operate in series, in which case two or more fans blow the same mass of air at different locations along the air stream.
An example of a serial fan system is provided in U.S. Pat. No. 5,546,272, issued to Moss, et al., which is incorporated herein by reference in its entirety and in a manner consistent with the present invention. In Moss (xe2x80x2272), two fans are provided at different locations along a common plenum. The fans are selected such that if one fan fails, the remaining fan will continue to provide adequate cooling, however, the patent does not provide for a high level of serviceability. Moss (xe2x80x2272) fails to disclose an apparatus having a fan assembly comprising several fans in parallel being in series with a second fan assembly comprising several fans in parallel.
An example of a parallel fan system is provided in U.S. Pat. No. 6,031,717, issued to Baddour, et al., which is incorporated herein by reference in its entirety and in a manner consistent with the present invention. In Baddour, several fans are placed to provide parallel airflow to a housing. Baddour recognizes that a failed fan will cause a xe2x80x9cshort circuitxe2x80x9d in the cooling system by allowing air to recirculate back out of the failed fan opening. To prevent such problems, Baddour provides a flexible one-way flap that closes off the opening of a failed fan. Baddour fails to disclose a second assembly of parallel fans being located in series with the first assembly of parallel fans, and fails to disclose a common plenum connecting two assemblies of parallel fans.
U.S. Pat. No. 5,745,041, issued to Moss, discloses an apparatus for supplementing the airflow provided by an internal main cooling fan of a computer power supply. The apparatus has two or more fans arranged in parallel or series, which are installed in a plenum that fits over the power supply housing. In the case where parallel fans are used, each fan has a separate well portion of the plenum that defines the space between the main fan and each fan of the apparatus. Each fan, including the internal main fan has sufficient capacity to cool the system, providing several levels of redundancy, but there is no disclosure of providing serviceability features to allow quick replacement of a failed fan. Moss (""041) also fails to disclose an apparatus having a fan assembly comprising several fans in parallel being connected by a plenum in series with a second fan assembly comprising several fans in parallel. Moss (""041) also fails to disclose an apparatus that may be used with high voltage electrical devices.
Therefore, it is desirable to provide an apparatus for cooling electrical devices that provides adequate cooling, even when one of the components fails. It is also desirable for such an apparatus to have a highly serviceable construction to allow for quick and easy assembly and replacement of inoperable components, which may be accomplished with little or no downtime of the device being cooled by the apparatus. It is also desirable for such a cooling system to be able to cool high-voltage electrical devices, to operate efficiently, and to operate quietly.
The present invention overcomes the problems discussed above, and provides additional advantages, by employing an apparatus for providing a supply of air for cooling electrical devices that comprises an assembly of parallel fans arranged in series with another assembly of parallel fans.
In one embodiment of the invention, an apparatus for providing a supply of air for cooling electrical devices includes a first fan housing, a second fan housing, and a balancing plenum connecting the first fan housing to the second fan housing. The first and second fan housings each have an open intake side and an open exhaust side, with the remainder of each hosing being substantially airtight. Each fan housing has a fan assembly in it. Each fan assembly has two or more fans, each of which is connected to a power supply, arranged to blow air in a parallel fashion. The fan assemblies are arranged to bring air in from the intake side of each fan housing and force it out of the exhaust side of each fan housing. The exhaust side of the first fan housing is attached, by the balancing plenum, to the intake side of the second fan housing, thereby arranging the two fan housings and the fans within them in series and creating a substantially airtight passage between the intake side of the first fan housing and the exhaust side of the second fan housing. The embodiment provides an adequate air supply when at least one fan is inoperable.
In one embodiment, the present invention may be used to cool high-voltage electrical devices. In one embodiment of the invention, the apparatus may be used to cool electrical power generation devices, such as the power bridge of an exciter for a power generator. In another embodiment of the invention, each fan assembly may have two fans. In another embodiment of the invention, each fan assembly may have three fans. In another embodiment of the invention, each fan assembly may have two sets of two fans. In yet another embodiment, each of the fans may be part of an individually-replaceable modular fan unit.
In one embodiment of the invention, a fan may be replaced without turning off the device that is being cooled by the apparatus. In another embodiment, a fan may be replaced in less than about three minutes.
In another embodiment of the invention, the fan housings and the balancing plenum may be made as integral units.
The present invention also comprises of a method for providing a supply of air for cooling electrical devices in which two or more sets of fan assemblies, which blow air in parallel fashion, are located in a series relationship with one another.